PAT CALDWELL

Hazards

No high surf advisory or warnings.

Forecast

Surf along south facing shores will be 2 to 4 feet through tonight, then will increase to 3 to 5 feet Friday.
Surf along east facing shores will be 3 to 5 feet through early Friday, then will decrease to 2 to 4 feet late Friday.
Surf along north facing shores will be 2 feet or less through Friday.
Surf along west facing shores will be 3 feet or less through Friday.

Outlook

Outlook through Thursday August 24: Surf is expected to trend down along east facing shores this weekend as the trades weaken slightly. A small south-southeast swell is expected to peak late Friday, and then gradually subside this weekend. A small, long-period southwest swell is forecast to arrive Saturday, and continue into early next week. Surf will likely remain below the High Surf Advisory criteria along all shores through the middle of next week.
Surf heights are forecast heights of the face, or front, of waves. The surf forecast is based on the significant wave height, the average height of the one third largest waves, at the locations of the largest breakers. Some waves may be more than twice as high as the significant wave height. Expect to encounter rip currents in or near any surf zone.

About Collaborative Surf

This collaborative forecast will be updated Monday through Friday at
300 PM when Pat Caldwell is available.

Collaborative Surf Table

FORECASTDATE

SWLHGT

DMNTDIR

DMNTPD

H1/3

H1/10

HGTTEND

PROB

WINDSPD

WINDDIR

SPDTEND

1PM08/16

6

ENE

8

3

5

SAME

13-19

ENE

DOWN

1

S

16

2

3

SAME

THU08/17

5

ENE

8

3

4

DOWN

LOW

12-18

ENE

DOWN

1

S

14

2

3

DOWN

LOW

1

SSE

17

2

4

UP

LOW

FRI08/18

4

ENE

8

2

3

DOWN

LOW

11-16

ENE

DOWN

2

SSE

15

3

5

UP

LOW

SAT08/19

4

E

7

1

2

DOWN

LOW

11-16

E

SAME

2

SSE

14

3

5

DOWN

LOW

SUN08/20

4

E

7

1

2

SAME

LOW

11-16

E

SAME

2

SSE

12

2

4

DOWN

LOW

MON08/21

5

E

8

2

4

UP

LOW

11-16

E

SAME

2

SE

10

2

3

SAME

LOW

Collaborative Surf Table Legend

LEGEND:

SWL HGT

Open ocean swell height measured from trough to crestin feet located 20 nautical miles offshore

DMNT DIR

Dominant direction typically +/-10 degrees in 16 compasspoints

DMNT PD

Dominant period in seconds

H1/3

Significant wave height in the surf zone

H1/10

Average height in the highest one-tenth waves in the surfzone

HGT TEND

Height tendency of swell (valid values: UP/DOWN/SAME)

PROB

Probability of occurrence (valid values: HIGH/MED/LOW)

WIND SPD

Open water wind speed measured in knots located20 nautical miles offshore

WIND DIR

Wind direction in 16 compass points

SPD TEND

Wind speed tendency (valid values: UP/DOWN/SAME)

Disclaimer

Surf heights will vary between different beaches and at the same
beach at different break areas.

Collaborative Surf Discussion

DISCUSSION:
SUMMARY:.
Summer surf from E and S.
DETAILED:.
Mid Wednesday on has breakers from 50-90 degrees
at levels near the trade windswell average. A decrease is
predicted for Thursday.
Surface high pressure near 40N, 140W is weakening and drifting
east. ASCAT satellite still showed some pockets to fresh trades
well ENE of Hawaii into Tuesday night. This should keep the
dominant wave period near the 8 second mark, which is elevated
enough to allow declining surf into Friday from within 50-90
degrees. Breakers should be near a trade windswell minimum by
Saturday.
See the latest NWS State Forecast Discussion regarding the trend
in trades. An area of enhanced tropical convection SE of the Big
Island is being monitored for influence on local wind, weather,
and waves for Sunday into Monday. A nominal local wind estimate is
given in the table above for 8/20-21. Stay tuned for updates.
Mid Wednesday on has near nil surf except for
locations susceptible to trade windswell. Similar conditions are
expected for Thursday.
No surf is expected in Hawaii from tropical cyclone Banyan in the
NW Pacific.
Mid Wednesday on has infrequent breakers from
170-190 degrees at levels below the summer average. Similar surf
is likely for Thursday.
The austral polar jet stream steered a low pressure system
hugging Antarctica eastward across the Hawaii SSW to S swell
window 8/7-8. Buoys 51004 to the SE of Hawaii is showing the most
energy in the 15-16 second band relative to 51002 and 51003,
indicating the event mostly missing Hawaii to the east. Since the
dominant wave periods are still elevated, there should be one more
day of similar or slightly less surf from this source.
This same low pressure tracked NE 8/9 and occluded 8/10 to the SE
of French Polynesia. A compact area of severe gales to storm-force
winds aimed at Hawaii over the 155-165 degree band. The system
weakened 8/11-12.
The swell source had French Polynesia on its path to Hawaii.
These islands cause partial shadowing and increase error bars for
the local surf estimate.
Long-period forerunners are due on Oahu Thursday 8/17 from 155-170
degrees. It should be filled in by Friday...peaking late Friday
near the summer average, and dropping slowly into Sunday. Surf
should return to the southern hemisphere trade windswell as the
dominant source by Monday.
Into the long range, a strong high pressure south and a
subtropical low ESE of French Polynesia has set up strong trades
within 20-30S, 135-150W 8/14-16. It is expected to last another
few days. This should be the dominant background surf next week
8/22-25 from 140-160 degrees. This event should be a notch larger
than the typical austral trade windswell.
Models show an increase in trades E to NE of Hawaii 8/21-23, that
should trend up breakers from windswell out of 50-90 degrees at
the same time.
This collaborative forecast will resume on Friday, August 18.
This forecast was produced through the collaborative efforts of
NWS and NCEI. Please send suggestions to w-hfo.webmaster@noaa.gov
or call the Warning Coordination Meteorologist at 808-973-5275.
ADDITIONAL RESOURCES:
See http://www.prh.noaa.gov/hnl/pages/marine.php